With such an arrangement, the dashboard body is provided with a window that is closed in its top face by a flap, and it is also provided with a firing channel that is fastened to the bottom face of the dashboard body while also surrounding the window.
The firing channel presents a top face that matches the convex shape of the dashboard body, and a bottom face that is generally plane and to which a standard type of airbag module is fastened.
When the airbag inflates, it passes through the firing channel so as to bear against the bottom face of the flap, thereby causing the flap to open. The airbag then passes through the window of the dashboard body so as to be deployed into the vehicle cabin for the purpose of protecting the occupants therein.
In general, the window is rectangular in outline and the flap is hinged about the transverse edge of the window that is closer to the front in the forward direction of the vehicle, i.e. the transverse edge that is closer to the windshield.
Given the speed with which the flap opens, it can strike against the windshield while it is opening as a result of the airbag inflating. This can give rise to flap debris being projected towards the occupants of the vehicle, and that might injure them.
In order to remedy that drawback, document U.S. Pat. No. 6,390,497 teaches that it is known to provide two lateral ties, each securing a respective side edge of the flap to a corresponding side edge of the window, those ties being slack while the flap is closed. The opening of the flap is then limited by the lateral retaining ties, which become tensioned as the airbag inflates so that the flap cannot strike the windshield.
The forces that arise during opening are large because it is desirable for the airbag to deploy rapidly, and as a result the mechanical strength of the retaining ties is generally not sufficient. In practice, the ties tend to be torn out from the dashboard body, thereby damaging the flap and as a result running the risk of projecting debris towards the occupants of the vehicle.